It is a well-established technique to provide reactive power support to a power grid from a wind turbine. Reactive power support is typically provided in case the grid voltage for some reasons decreases.
However, according to traditional methods fast reactive power support may be difficult, if not impossible, to provide if the wind turbine selected for this purpose is already being operated at or near its rated power level. The reason for this mainly being that the overall current limit of the selected wind turbine may be exceeded if the reactive power support is launched while the wind turbine is already being operated at or near its rated power level. Obviously, exceeding the current limit of the wind turbine might damage the wind turbine.
Traditional methods solve the current limit problem by slowly derating the selected wind turbine. However, this typically leads to unwanted grid instability as well as an increased rotor speed which has to be dealt with by pitching the rotor blades out of the wind in order to match the wind power input with the derated power level.
It may be seen as an object of embodiments of the present invention to provide a method for providing a fast reactive power support even though the wind turbine is operated at its rated power level.